The Pleistocene marine beds of Ontario have been studied for many years and have yielded a great number of fossils at different points along the Saint Lawrence and Ottawa and in the country between these two rivers, as well as along the rivers flowing north into Hudson bay,* proving that the sea once occupied these regions for a length of time sufficient to form beds of clay and sand often more than 100 feet thick. Sir William Dawson has divided these deposits into “Leda clay” and “Saxicava sand,” the names being derived from the commonest fossils occurring in them. The Leda clay usually rests on boulder-clay, and the Saxicava sand usually overlies the Leda clay, so that in general one may say that the stratified marine beds were formed later than the last retreat of the ice from the region mentioned.
Probably the beds most productive in fossils . . .